undici or node native fetch is not working with mTLS

Bug Description

this works with node-fetch

import https from 'https';

const agent = new https.Agent({
    key,
    cert,
    rejectUnauthorized: false,
    keepAlive: true,
  });

this does not work

import { Agent } from 'undici';

dispatcher: new Agent({
      connect: {
        cert: cert,
        key: key,
        rejectUnauthorized: false,
        keepAlive: true,
      },
    })

Reproducible By

You can use this repo https://github.com/sibelius/node-mtls

to create cert, key for a server and for a client

Expected Behavior

mTLS should work with undici and node native fetch

Logs & Screenshots

FETCH 604571: request to GET https://endpoint errored - read ECONNRESET

Environment

System:
OS: Linux 6.8 Ubuntu 24.04.1 LTS 24.04.1 LTS (Noble Numbat)
CPU: (12) x64 Intel(R) Xeon(R) Platinum 8160 CPU @ 2.10GHz
Memory: 52.21 GB / 64.00 GB
Container: Yes
Shell: 5.2.21 - /bin/bash
Binaries:
Node: 22.13.0 - ~/.nvm/versions/node/v22.13.0/bin/node
npm: 10.9.2 - ~/.nvm/versions/node/v22.13.0/bin/npm
pnpm: 9.15.4 - ~/.nvm/versions/node/v22.13.0/bin/pnpm

Additional context

trying to make undici mTLS work

Start with the provided sibelius/node-mtls repository to reproduce the ECONNRESET case on Node 22, then inspect the undici Agent connect options used with native fetch and compare them with the working node-fetch https.Agent example. Done means the same mTLS certificates work successfully with undici and Node native fetch.